MONDAY, April 19 (HealthDay News) -- Statins don't lower the risk of colorectal cancer, and may even increase the chances of developing precancerous polyps, new research suggests.

Statins are widely prescribed cholesterol-lowering drugs sold in a variety of generic forms and brand names, including Lipitor, Crestor and Zocor.

Yet, researchers stressed that the results are "not conclusive," and that people taking statins to lower cholesterol and reduce their risk of heart attack should continue taking the drugs.

"We found patients in this study taking statins for more than three years tended to develop more premalignant colon lesions," said study author Dr. Monica Bertagnolli, chief of the division of surgical oncology at Brigham and Women's Hospital and a professor of surgery at Harvard Medical School. "This is an interesting finding that needs to be followed up, but it should not raise alarm. No one should stop taking their statins."

The study is to be presented Monday at the American Association for Cancer Research annual meeting in Washington, D.C., and it is also published online in the journal Cancer Prevention Research.

The data used in the analysis was from an earlier clinical trial to determine if the cox-2 painkiller celecoxib (Celebrex) could be used to prevent colon cancer. That trial included 2,035 people who were at high risk of colon cancer and had already been diagnosed with precancerous polyps, or adenomas.

That study, published in 2006, found the celecoxib reduced the occurrence of adenomas, but it also more than doubled the risk of heart attack and other serious cardiac events.

As a result, celecoxib is not used to prevent colon cancer, though it is still prescribed for its original use, to treat arthritis.

About 36 percent of the people in the trial also happened to be taking statins, enabling researchers to go back and see if statin use had any effect on developing adenomas.

The researchers found that patients who had been in the placebo group and who used statins at any time were no less likely to develop adenomas over a five-year period compared with those patients who never used statins.

For those who took statins for three years or longer, the chances of developing the adenomas were nearly 40 percent higher than those not on statins. Those taking celecoxib and statins did not have an increased chance of developing adenomas, probably because the anti-tumor effects of celecoxib canceled out any tumor-promoting effect of the statins, according to the study.

While statins aren't helpful in preventing colorectal cancer, experts from the American Cancer Society also urged people to continue taking statins for cardiovascular health.

"The suggestion of higher risk of colorectal polyp recurrence among a subgroup of statin users in this study may be due to chance and should not raise concerns," said Eric Jacobs, the American Cancer Society's strategic director of pharmacoepidemiology. "A similar previous study of polyp recurrence did not find higher risk among statin users. Statins are valuable drugs, proven to reduce risk of heart disease. Results of this study should not influence decisions about statin use."

For now, the best way to prevent colon cancer is to make sure you get a colonoscopy screening at age 50, or earlier for those with a family history, Bertagnolli said.